More polish in prep for CrOS support

tools/gpu/gpu_tools/scroll.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Inject this script on any page to measure framerate as the page is scrolled
 // from top to bottom.
 //
 // Usage:
 //   1. Define a callback that takes a RenderingStats object as a parameter.
 //   2. To start the test, call new __ScrollTest(callback).
@@ skipping 104 matching lines @@
     requestAnimationFrame(this.recordFrameTime_.bind(this));
   }
 
   RafRenderingStats.prototype.stop = function() {
     this.recording_ = false;
   }
 
   RafRenderingStats.prototype.get = function() {
     var results = {};
     results.numAnimationFrames = this.frameTimes_.length - 1;
-    results.numFramesSentToScreen = results.numFramesSentToScreen;
+    results.numFramesSentToScreen = results.numAnimationFrames;
     results.droppedFrameCount = this.getDroppedFrameCount_(this.frameTimes_);
     results.totalTimeInSeconds = (
         this.frameTimes_[this.frameTimes_.length - 1] -
         this.frameTimes_[0]) / 1000;
     return results;
   };
 
   RafRenderingStats.prototype.recordFrameTime_ = function(timestamp) {
     if (!this.recording_)
       return;
@@ skipping 46 matching lines @@
     // ensures this method will be called after the document is loaded.
     this.element_ = opt_element || document.body;
     // Some pages load more content when you scroll to the bottom. Record
     // the original element height here and only scroll to that point.
     this.scrollHeight_ = this.element_.scrollHeight
     requestAnimationFrame(this.startPass_.bind(this));
   };
 
   ScrollTest.prototype.startPass_ = function() {
     this.element_.scrollTop = 0;
-    if (window.chrome && chrome.gpuBenchmarking)
+    if (window.chrome && chrome.gpuBenchmarking &&
+        chrome.gpuBenchmarking.renderingStats)
       this.renderingStats_ = new GpuBenchmarkingRenderingStats();
     else
       this.renderingStats_ = new RafRenderingStats();
     this.renderingStats_.start();
 
     this.gesture_ = new SmoothScrollDownGesture(this.element_,
                                                 this.isGmailTest_);
     this.gesture_.start(this.onGestureComplete_.bind(this));
   };
 
@@ skipping 26 matching lines @@
       console.log(this.renderingStats_.get());
   };
 
   ScrollTest.prototype.endPass_ = function() {
     this.renderingStats_.stop();
   };
 
 
   window.__ScrollTest = ScrollTest;
 })();